With the acceleration of global climate change and urbanization, extreme weather occurs frequently. The urban ecological environment’s quality declines—urban green space as the core of urban ecological function and environmental service. The urban green space plants threatened by extreme climate, such as dry and withered, ice and snow damaged, etc. So, it is necessary and urgent to strengthen the response research of urban green space to extreme climate. This paper takes the harsh drought climate suffered by Nanchang city in 2019 as an example to analyze the tree species under drought stress in the urban green space of Nanchang city. The results show that: (1) Among the trees surveyed, the ones that are affected by drought stress are those with smaller crowns and shorter heights. (2) Compared with deciduous tree species, evergreen species have more leaves and are not easy to fall off. Drought stress occurs in the higher temperature period of Nanchang, which further intensifies the transpiration, and the response of evergreen tree species to drought stress is more prominent. In the planting of evergreen trees, the proportion of coniferous trees should appropriately increase. (3) The spatial environment of urban green trees affects the response of trees to drought stress. The setting of small confined space limits trees’ growth, and trees in an unhealthy state are more vulnerable to drought stress. (4) Urban green space will be regularly pruned, irrigated, fertilized, and exerted other management measures, effectively reducing the impact of drought stress on urban green space.